KINETIC-ANALYSIS OF LIVING POLYMERIZATION PROCESSES EXHIBITING SLOW EQUILIBRIA .5. EFFECT OF MONOMER TRANSFER IN CATIONIC POLYMERIZATION AND SIMILAR LIVING PROCESSES

This work deals with the kinetics of polymerization processes with cha in transfer to monomer and reversible formation of dormant species. Su ch a mechanism is typical for cationic polymerization in the presence of Lewis acids as co-initiators. The expressions of number- and weight -average degrees of polymerization and polydispersity index are derive d rigorously for a mechanism with free ions as the active species, but it is also applied to other mechanisms, e.g., ion pairs as active spe cies. Plots of polydispersity index versus monomer conversion can be e asily computed on a PC computer even though the expressions for the we ight-average degree of polymerization and the concentration of residua l initiator consist of confluent hypergeometric functions. Numerical c alculations show that the polydispersity index of the resulting polyme r approaches M(w)/M(n) = 2 with increasing rate constant of chain tran sfer. Addition of common ions led to narrower molecular weight distrib utions. For the polymerization of indene with the cumyl chloride/titan ium tetrachloride initiating system in methylene chloride, the calcula ted results of number-average degree of polymerization are in agreemen t with the experimental data reported in the literature.